The three most common chronic obstructive pulmonary diseasesemphysema, chronic bronchitis, and asthmaall present a confusingly similar symptom picture. Dyspnea, difficulty in moving air through the airways, chest tightness, and wheezing are common with all three. Coughing is a basic symptom of chronic bronchitis, and frequent with the other two. The airway hyperreactivity of asthma often appears when chronic bronchitis temporarily worsens.

These similarities muddied the diagnostic waters for a very long time. Back in 1794, the distinguished 18th-century Edinburgh physician William Cullen complained that: "The term asthma has been commonly applied . . . , even by many . . . specialists, to every case of difficult breathing. ... By not distinguishing it with sufficient accuracy from other cases of Dyspnea, they have introduced a great deal of confusion into their treatises on this subject." The road leading to accurate diagnosis of the COPD entities opened up when the French physician Laennec developed the stethoscope early in the nineteenth century.

The principles of treatment for each COPD entity are also very similar. Therapy is aimed primarily at decreasing or reversing the airflow obstruction created by abundant mucus secretion, and/or hyperinflation, and/or airway muscle contraction, and/or other inflammatory processes.

If the goal of therapy